FRIDAY, March 30, 2018 (HealthDay News) -- Lung cancer death rates among women have fallen in much of the United States, but have increased in two regions where smoking is more common, a new study finds.

The first cluster or "hot spot" comprises 669 counties in Appalachia and the Midwest, and the second is 81 counties in the northern Midwest, according to the analysis of U.S. National Cancer Institute data.

Nationwide, the rate of lung cancer death among women fell 6 percent between 1990 and 2015.

But rates rose 13 percent in the first hot spot and 7 percent in the second one during this time period, according to the researchers.

"Midwestern and Appalachian states have the highest prevalence of smoking among women and the lowest percent declines in smoking in recent years, so it is perhaps not surprising that we found that women in these areas experienced a disparity in lung cancer death rates," said study co-author Katherine Ross.

She is a graduate student in Emory University's Rollins School of Public Health in Atlanta.

In 1990, the lung cancer death rate among women in the largest hot spot was 4 percent lower than that for women in the rest of the United States. By 2015, it was 28 percent higher, the study found.

For the second hot spot, women's lung cancer death rate was 18 percent lower than elsewhere in 1990, but rose to the same as non-hot spot levels by 2015.

The study was published March 30 in the journal Cancer Epidemiology, Biomarkers & Prevention.

Ross warned that the geographic differences may get worse unless tobacco use among women in these hot spots is reduced.

"There are several effective tobacco control policies available, such as increased excise taxes on tobacco and comprehensive smoke-free air laws that ban smoking in the workplace, restaurants and bars," Ross said in a journal news release.

"However, many states in our identified hot spots either do not have these measures in place, or they are comparatively weak and could be strengthened," she added.